Hi,
I am a new learner of join command. Some result really make me confused.
Please kindly help me.
input:
file1:
LEO oracle engineer 210375
P.Jones Office Runner ID897
L.Clip Personl Chief ID982
S.Round UNIX admin ID6
file2:
Dept2C ID897 6 years
Dept5Z ID982 1 year
Dept3S ID6 2... (1 Reply)
example sql:
select a.a1,b.b1,c.c1,d.d1,e.e1
from a
left outer join b on a.x=b.x
left outer join c on b.y=c.y
left outer join d on d.z=a.z
inner join a.t=e.t
I know how single outer or inner join works in sql.
But I don't really understand when there are multiple of them.
can... (0 Replies)
Hello,
My apologies if this has been posted elsewhere, I have had a look at several threads but I am still confused how to use these functions. I have two files, each with 5 columns:
File A: (tab-delimited)
PDB CHAIN Start End Fragment
1avq A 171 176 awyfan
1avq A 172 177 wyfany
1c7k A 2 7... (3 Replies)
I have to join(no other command is allowed) 3 files together. And im aware that i have to sort these files(file1 file2 file3) first before I can join them.
However i have to output these sorted files to some temporary file. i can't just do sort -n file1 > file1 or i get an empty file output. Is... (3 Replies)
Hi,
I have 20 tab delimited text files that have a common column (column 1). The files are named GSM1.txt through GSM20.txt. Each file has 3 columns (2 other columns in addition to the first common column).
I want to write a script to join the files by the first common column so that in the... (5 Replies)
Hi team
Optimizer max permutations and search limit are set to 3.5 million and 10 respectively.The parameter instruct optimizer to evaluate up to 3.5 million permutations for max 10 table joins
I have query with 9 tables joined.
How many combinations will optimizer perform to find best... (1 Reply)
Hello,
This post is already here but want to do this with another way
Merge multiples files with multiples duplicates keys by filling "NULL" the void columns for anothers joinning files
file1.csv:
1|abc
1|def
2|ghi
2|jkl
3|mno
3|pqr
file2.csv:
1|123|jojo
1|NULL|bibi... (2 Replies)
Discussion started by: yjacknewton
2 Replies
LEARN ABOUT MOJAVE
fields
fields(3pm) Perl Programmers Reference Guide fields(3pm)NAME
fields - compile-time class fields
SYNOPSIS
{
package Foo;
use fields qw(foo bar _Foo_private);
sub new {
my Foo $self = shift;
unless (ref $self) {
$self = fields::new($self);
$self->{_Foo_private} = "this is Foo's secret";
}
$self->{foo} = 10;
$self->{bar} = 20;
return $self;
}
}
my $var = Foo->new;
$var->{foo} = 42;
# this will generate an error
$var->{zap} = 42;
# subclassing
{
package Bar;
use base 'Foo';
use fields qw(baz _Bar_private); # not shared with Foo
sub new {
my $class = shift;
my $self = fields::new($class);
$self->SUPER::new(); # init base fields
$self->{baz} = 10; # init own fields
$self->{_Bar_private} = "this is Bar's secret";
return $self;
}
}
DESCRIPTION
The "fields" pragma enables compile-time verified class fields.
NOTE: The current implementation keeps the declared fields in the %FIELDS hash of the calling package, but this may change in future
versions. Do not update the %FIELDS hash directly, because it must be created at compile-time for it to be fully useful, as is done by
this pragma.
Only valid for perl before 5.9.0:
If a typed lexical variable holding a reference is used to access a hash element and a package with the same name as the type has declared
class fields using this pragma, then the operation is turned into an array access at compile time.
The related "base" pragma will combine fields from base classes and any fields declared using the "fields" pragma. This enables field
inheritance to work properly.
Field names that start with an underscore character are made private to the class and are not visible to subclasses. Inherited fields can
be overridden but will generate a warning if used together with the "-w" switch.
Only valid for perls before 5.9.0:
The effect of all this is that you can have objects with named fields which are as compact and as fast arrays to access. This only works as
long as the objects are accessed through properly typed variables. If the objects are not typed, access is only checked at run time.
The following functions are supported:
new perl before 5.9.0: fields::new() creates and blesses a pseudo-hash comprised of the fields declared using the "fields" pragma into
the specified class.
perl 5.9.0 and higher: fields::new() creates and blesses a restricted-hash comprised of the fields declared using the "fields" pragma
into the specified class.
This function is usable with or without pseudo-hashes. It is the recommended way to construct a fields-based object.
This makes it possible to write a constructor like this:
package Critter::Sounds;
use fields qw(cat dog bird);
sub new {
my $self = shift;
$self = fields::new($self) unless ref $self;
$self->{cat} = 'meow'; # scalar element
@$self{'dog','bird'} = ('bark','tweet'); # slice
return $self;
}
phash
before perl 5.9.0:
fields::phash() can be used to create and initialize a plain (unblessed) pseudo-hash. This function should always be used instead of
creating pseudo-hashes directly.
If the first argument is a reference to an array, the pseudo-hash will be created with keys from that array. If a second argument is
supplied, it must also be a reference to an array whose elements will be used as the values. If the second array contains less
elements than the first, the trailing elements of the pseudo-hash will not be initialized. This makes it particularly useful for
creating a pseudo-hash from subroutine arguments:
sub dogtag {
my $tag = fields::phash([qw(name rank ser_num)], [@_]);
}
fields::phash() also accepts a list of key-value pairs that will be used to construct the pseudo hash. Examples:
my $tag = fields::phash(name => "Joe",
rank => "captain",
ser_num => 42);
my $pseudohash = fields::phash(%args);
perl 5.9.0 and higher:
Pseudo-hashes have been removed from Perl as of 5.10. Consider using restricted hashes or fields::new() instead. Using
fields::phash() will cause an error.
SEE ALSO
base
perl v5.18.2 2014-01-06 fields(3pm)